Enquire within upon everything.

  • Robert Kemp Philp
Date:
1863
Catalogue details

Licence: Public Domain Mark

Credit: Enquire within upon everything. Source: Wellcome Collection.

Provider: This material has been provided by The University of Leeds Library. The original may be consulted at The University of Leeds Library.

    90/392 page 54
    mixtures which axe to be found de- scribed in books, are incorrectly so named, for although they themselves become colder than freezing, yet they are not sufficiently powerf^ to freeze any quantity of water, or other sub- stances, when placed in a vessel within them. In order to be efficient as a freezing mixture, as distinguished from a cooling one, the materials used ought to be capable of producing by them- selves an amount of cold more than thirty degrees below the freezing point of water, and this the ordinary mix- tures will not do. Much more efficient and really freezing mixtures may be made by using acids to dissolve the salts. The cheapest, and perhaps the best, cf these for ordinary use, is one which is frequently employed in France, both for making dessert ices, and cooling wines, &c. It consists of coarsely powered glauber salt (sulphate of soda), on which is poured about tv.ro-thirds its weight of spirits of salts (muriatic acid). The mixtiire should be made in a wooden vessel, as that is preferable to one made of metal, which conducts the external heat to the ma- terials with great rapidity; and when the substance to be cooled is placed in the mixture, the whole should be covered with a blanket, a piece of old woollen carpet doubled, or some other non-conducting material, to prevent the access of the external warmth; the vessel used for icing wines should not be too large, that there may be no waste of the freezing mixture. This combination produces a degree of cold thirty degrees below freezing; and if the materials are bought at any of the wholesale druggists or diysalters, it is exceedingly economical. It is open, however, to the very great objection, that the muriatic acid is an exceedingly corrosive liquid, and of a pungent, disagreeable odour; this almost pre- cludes its use for any purposes except that ofricing wines. Another substance, which is free from any corrosive action or unplea- sant odour, is the nitrate of ammonia, which, if simply dissolved in rather less than its own weight of water, re- duces the temperature to about twenty- five degrees below freezing. The ob- jections to its use are, that its frigorific power is not sufficiently great to freeze readily; and if it is required to form dessert ices, it is requisite to renew the process at the expiration of a quarter of an hour, a second, or even, if the weather is very hot, and the water used is rather warm, a third or fourth time. Again the nitrate of ammonia is a very expensive salt; even in France, where it is manufactured expressly for this purpose, it is sold at the rate of thi-ee francs a poimd; and in this covmtiy it cannot be obtained imder a much higher price. One great re- commendation, however, attends its use, namely, that it may be recovered again, and used any number of times, by simply boiling away the water in which it is dissolved, by a gentle fire, imtil a small portion, on being removed, crystallises on cooling. If, however, nitrate of ammonia in coarse powder is put into the cooler, and there is then added twice its weight of freshly crushed washing soda, and an equal quanti ty of the coldest water that can be obtained, an intensely powerful frigorific mixture is the re- sult, the cold often falling to forty degrees below freezing. This is by far the most efficacious freezing mixture that can be made without the use of ice or acids. But, unfortunately, it has an almost insuperable objection, that the nitrate of ammonia is decom- posed by the soda, and cannot be recovered by evaporation; this rises the expense to so great a height, that the plan is practically useless. The New Fbeezinq Preparation WITHOUT Ice or Acids obviates all these objections. It is easy of use, not corrosive in its properties, and capable of being used at any time, at a minute’s notice; is easy of transport, being in a solid form, and, moreover, moderate in its cost. In India, to which country it baa been exported in
    digitised image 1
    digitised image 2
    digitised image 3